| abstract |
To provide a new positive electrode active material for providing a lithium ion secondary battery excellent in capacity. What is claimed is: 1. A positive electrode active material, which has a crystal structure that can be assigned to a space group Fm-3m and is represented by the following composition formula (1). Li 1 + x Nb y Fe a Mn b P c X d O e (1) In the composition formula (1), X is selected from halogen elements. x, y, a, b, c, d and e are 0 <x <1, 0 <y <0.5, 0.25 ≦ a + b <1, 0 ≦ a <1, 0 ≦ b <1, 0 <C ≦ 0.05, 0 ≦ d ≦ 0.2, and 1.8 ≦ e ≦ 2.2 are satisfied. |